We aren't doctors and can't try to guess at a diagnosis, but as I said above it's not likely anything serious. But it's impossible to be certain without a professional exam. Just do it. You're never going to get a clear answer by online searching or forums.
Is there something serious that I could be?
First, this of course cannot be an STD, since you hae nod no sexual contact with another person.
Second, it probably isn't serious -- most likely some sort of normal anatomic variant, cyst, or something like that. Almost certainly not cancer or anything else dangerous.
Third, you should see your doctor. You can also safely tell your parents; there is nothing at all in this that should be embarrassing or that has implications that could embarrass you. (For example, it has absolutely nothing to do with masturbating.) But if you can't talk with your mom or dad about it, you still can get checked confidentially and without their knowledge at a Planned Parenthood clinic, local health department clinic, or community clinic. (But the best choice would be your own doctor and with your parents' knowledge.)
In the meantime, try not to worry! Almost certainly this will turn out to be no big deal!